太阳系小天体表面环境综述

地面和空间望远镜观测,特别是最近30多年来的历次深空探测任务极大提高了我们对太阳系小天体的认识。现已知小天体表面具有复杂多样的形貌特征,这些特征与其历史上所经历过的地质演变有密切关系,亦可为理解早期太阳系的动力学环境提供重要信息。文章首先简要介绍了通过天文观测数据反演小行星形貌信息的基本原理和方法;然后基于已实施的深空探测任务获取的数据资料,回顾和总结了433 Eros、25143 Itokawa、4179 Toutatis、162173 Ryugu、101955 Bennu及486958 2014 MU69这6颗小行星的表面环境和物理性质,其中着重介绍了对这几颗小行星的形状、表面碎石形态和分布、撞击坑形貌和分布、表面坡度、沟槽和山脊等线性结构以及表壤运动痕迹等的认识,以及如何根据这些信息推测各小行星的形成历史;最后简要介绍了目前认为可能影响小行星表面形貌的几种机制,以期为我国即将开展的小天体深空探测任务提供借鉴。     

铝锂合金高速铣削表面粗糙度试验研究

在对2198铝锂合金进行高速铣削试验的基础上,研究了切削参数对表面粗糙度的影响规律,观察了其铣削表面形貌。结果表明:平直处表面粗糙度与拐角处表面粗糙度不一致是由机床主轴振动和实际进给量变化造成的;较小的每齿进给量和铣削宽度能够获得较好的表面质量;表面缺陷常发生在铣削刀痕交叉处。     

整体叶盘叶片磨抛工艺参数优化

以整体叶盘作为加工对象,为提高其叶片表面加工质量,降低表面粗糙度,展开整体叶盘磨抛工艺参数(如砂带粒度、砂带线速度、进给速度)的优化.首先,进行整体叶盘数控磨抛试验,其次,应用信噪比优化磨抛工艺参数,最后,选最优工艺参数对整体叶盘进行磨抛试验,加工表面测量结果表明,整体叶盘表面粗糙度显著降低,满足叶盘表面加工质量要求.     

磨料形状对钛合金紧固件涂层结合力的影响

采用不同形状的磨料对钛合金紧固件进行粗化处理,并在表面制备涂层,检测不同工艺下的涂层结合力.通过粗糙度测试仪检测3种样品的表面粗糙度,采用扫描电镜观察对比3种样品的表面微观形貌,分析不同工艺处理的表面对结合力的影响.结果表明:砂粒喷射主要使基体产生一个冲切过程,较丸粒喷射,表面有更大的深度,表面粗化效果更明显,从而使得涂层与紧固件表面的结合面积增加,更有利于涂层与基体间结合力的提高.经砂粒喷射的钛合金紧固件的涂层结合力更优,满足标准要求.     

平面磨削石英陶瓷比磨削能正交试验研究

通过大量的正交试验,研究陶瓷材料在低速下的磨削性能,优化陶瓷磨削参数,对于丰富陶瓷磨削理论,指导实际生产实践具有重要的现实意义.     

Collaborative manufacturing technologies of structure shape and surface integrity for complex thin-walled components of aero-engine: Status,challenge and tendency

Presently, the service performance of new-generation high-tech equipment is directly affected by the manufacturing quality of complex thin-walled components. A high-efficiency and quality manufacturing of these complex thin-walled components creates a bottleneck that needs to be solved urgently in machinery manufacturing. To address this problem, the collaborative manufacturing of structure shape and surface integrity has emerged as a new process that can shorten processing cycles, improve machining qualities, and reduce costs. This paper summarises the research status on the material removal mechanism, precision control of structure shape, machined surface integrity control and intelligent process control technology of complex thin-walled components. Numerous solutions and technical approaches are then put forward to solve the critical problems in the high-performance manufacturing of complex thin-wall components. The development status, challenge and tendency of collaborative manufacturing technologies in the high-efficiency and quality manufacturing of complex thin-wall components is also discussed.     

如何提高飞机表面质量

探讨了提高飞机表面质量的方法。提出提高飞机表面质量是个系统工程,必须从优化设计结构、提高零件和工装的制造准确度及协调准确度,采用合理的铆接装配工艺方法等多方面共同采取措施。     

Influences of milling and grinding on machined surface roughness and fatigue behavior of GH4169 superalloy workpieces

Surface topography of superalloy GH4169 workpieces machined by milling and grinding is different significantly. Meanwhile, surface roughness, as one of the main indicators of machined surface integrity, has a great influence on the fatigue behavior of workpieces. Based on analyzing the formation mechanism and characteristics of surface roughness utilizing different machining processes and parameters, the machined surface roughness curve can be decoupled into two parts utilizing frequency spectrum analysis, which are kinematic surface roughness curve and stochastic surface roughness curve. The kinematic surface roughness curve is influenced by machining process,parameters, geometry of the cutting tool or wheel, the maximum height of which is expressed as R'_z.By subtracting the kinematic part from the measurement curve, the stochastic surface roughness curve and its maximum height R'_zcan be obtained, which is influenced by the defects of cutting tool edge or abrasive grains, built-up edges(BUE), cracks, high frequency vibration and so on. On the other hand, the results of decoupling analysis of surface roughness curves indicate that Raand Rz values of milling GH4169 are 2–5 times and 1–3 times as high as those of grinding, while R'_zvalue of milling is 13.85%–37.7% as high as that of grinding. According to the results of fatigue life tests of specimens machined by milling and grinding, it can be concluded that fatigue behavior of GH4169 decreases with the increase of R'_zmonotonically, even utilizing different machining processes.     

半主动寻的中程舰空导弹复合制导控制技术概述

介绍了采用垂直发射捷联惯导＋修正指令＋半主动寻的复合制导体制，并对所涉及的一系列制导与控制方面的技术关键及难点进行了讨论。     

Introduction to Japanese exploration study to the moon

The Japan Aerospace Exploration Agency (JAXA) views the lunar lander SELENE-2 as the successor to the SELENE mission. In this presentation, the mission objectives of SELENE-2 are shown together with the present design status of the spacecraft. JAXA launched the Kaguya (SELENE) lunar orbiter in September 2007, and the spacecraft observed the Moon and a couple of small satellites using 15 instruments. As the next step in lunar exploration, the lunar lander SELENE-2 is being considered. SELENE-2 will land on the lunar surface and perform in-situ scientific observations, environmental investigations, and research for future lunar utilization including human activity. At the same time, it will demonstrate key technologies for lunar and planetary exploration such as precise and safe landing, surface mobility, and overnight survival. The lander will carry laser altimeters, image sensors, and landing radars for precise and safe landing. Landing legs and a precisely controlled propulsion system will also be developed. A rover is being designed to be able to travel over a wide area and observe featured terrain using scientific instruments. Since some of the instruments require long-term observation on the lunar surface, technology for night survival over more than 2 weeks needs to be considered. The SELENE-2 technologies are expected to be one of the stepping stones towards future Japanese human activities on the moon and to expand the possibilities for deep space science.